HECTR1.5 (Hydrogen Event-Containment Transient Response) is a lumped-volume
containment analysis program that is most useful for performing parametric studies. Its main
purpose is to analyze nuclear reactor accidents involving the transport and combustion of
hydrogen, but HECTR can also function as an experiment analysis tool and can solve a limited
set of other containment problems. Six gases; steam, nitrogen, oxygen, hydrogen, carbon
monoxide, and carbon dioxide are modified along with sumps containing liquid water. HECTR
can model virtually all the containment systems of importance in ice condenser, large dry and
Mark III containments. A postprocessor, ACHILES1.5, is included. It processes the
time-dependent variable output (compartment pressures, flow junction velocities, surface
temperatures, etc.) produced by HECTR. ACHILES can produce tables and graphs of these data.

5. METHOD OF SOLUTION

To calculate the pressure, temperature, and composition of gases in a containment, the
system is divided into compartments with flow between compartments occurring at junctions.
Each compartment is essentially a gas control volume. Flows between compartments are pressure
and buoyancy driven with inertial and resistance terms included. Steam is treated as a real gas,
and the other gases are treated as ideal. Gases in each compartment are instantaneously mixed,
and source terms are user-specified. Simplified conservation equations are solved using a
linearized implicit formulation (backward Euler method) to determine compartment and junction
conditions during the transient. The linear system of equations that results from the linearized
implicit formulation is solved by standard LU decomposition followed by back substitution. The
thermal response of surfaces and equipment in the containment can also be calculated, using
either one-dimensional finite difference slabs or lumped masses. An improved heat conduction
model incorporated in HECTR1.5+ correctly accounts for heat conduction in a multilayered slab.
The effects of many important physical phenomena in reactor containments during accidents, as
well as many engineered safety features (ESF's), are modeled. The physical phenomena
considered are hydrogen combustion, radiative and convective heat transfer, steam condensation
or evaporation, and containment leakage. The ESF's modeled are containment sprays, fans, fan
coolers, ice condensers with doors, sumps, suppression pools, and heat exchangers.

6. RESTRICTIONS OR LIMITATIONS

Steam explosions, core-concrete interactions, and aerosol transport are not modeled by
HECTR. Distribution is limited to U. S. (USSO).

7. TYPICAL RUNNING TIME

NESC executed the HECTR1.5+ sample problem in 89 seconds on a DEC VAX11/785.

8. COMPUTER HARDWARE REQUIREMENTS

Approximately 1.7Mbytes of virtual memory are required on the DEC VAX11. The
HECTR1.5+ documentation states the code can execute on a Cray, Vax, CDC, and Cyber.

9. COMPUTER SOFTWARE REQUIREMENTS

HECTR requires a FORTRAN 77 compiler and ran under COS 1.11 on a Cray, and
under VMS 4.1operating systems on VAX computers.